The present invention relates generally to control system for internal combustion engines, and more particularly, to a high-resolution electronic throttle position system.
Many previously known motor vehicle throttle controls have a direct physical linkage between an accelerator pedal and the throttle so that the throttle plate is pulled open by the accelerator cable as the driver presses the pedal. The direct mechanical linkage includes a biasing force that defaults the linkage to a reduced operating position, in a manner consistent with regulations. Nevertheless, such mechanisms are often simple and unable to adapt fuel consumption efficiency to changing traveling conditions, and add significant weight and components to the motor vehicle.
An alternative control for improving throttle control and the precise introduction of fuel air mixtures into the engine cylinders is provided by electronic throttle controls. The electronic throttle control includes a throttle position controller that positions the throttle plate by an actuator controlled by a microprocessor based on the sensor feedback. The processors are often included as part of a powertrain electronic control that can adjust the fuel and air intake and ignition in response to changing conditions of vehicle operation as well as operator control. Protection may be provided so that an electronic system does not misread or misdirect the control and so that unintended operation is avoided when portions of the electronic control suffer a failure.
One previously known type of protection to avoid unintended actuation of excessive throttle is to employ sensor redundancies, whereby more than one sensor responds to a particular condition so that the failure of a single sensor or an electronic component does not induce a throttle position greater than commanded throttle position.
Typically, motorized throttle bodies have two throttle position sensors. One of those sensors (or an average of both) is used for feedback position control. The throttle position is encoded as a continuous voltage (normally zero to five volts). The voltage is read by an analog-to-digital converter with a fixed resolution (typically about five millivolts per A/D count over the range of five volts). Typically, the throttle position sensor has a gain that is approximately xe2x85x9th degree for every five millivolts. This results in a nominal fine motion control of xe2x85x9th degree equally over the entire range of the throttle plate. Unfortunately, fine motion control is most important where the throttle is the predominant air control. This occurs in approximately the first 10 degrees of throttle opening.
The disadvantages associated with these conventional electronic throttle position sensor techniques have made it apparent that a new technique for electronic throttle position sensing is needed. The new technique should allow higher resolution motion control than the prior art and should not add cost or reduce reliability. The present invention is directed to these ends.
It is, therefore, an object of the invention to provide an improved and reliable high-resolution electronic throttle position system. Another object of the invention is to provide higher resolution motion control than the prior art. An additional object of the invention is reduce overall electronic system cost while improving reliability.
In accordance with the objects of this invention, a high-resolution electronic throttle position system is provided. In one embodiment of the invention, a high-resolution position sensing apparatus for determining the angular position of a throttle plate located in an electronic throttle and controlled by a PCM includes a first throttle position sensor and a second throttle position sensor. The first throttle position sensor is coupled to the throttle plate and generates a first throttle position sensor output signal. The first throttle position sensor output signal is a negative slope signal and is affine to the position of the throttle plate from a full closed position to full open position. The second throttle position sensor is also coupled to the throttle plate and generates a second throttle position sensor output signal. The second throttle position sensor output signal is a positive slope signal and is affine to the position of the throttle plate from the full closed position to approximately half open. Because the second sensor is used over a smaller range it may be used to achieve a higher signal resolution over that smaller range.
The present invention thus achieves an improved high-resolution electronic throttle position system. The present invention is advantageous in that by using a high gain throttle position sensor the need for a PCM amplification circuit is eliminated.
Additional advantages and features of the present invention will become apparent from the description that follows, and may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims, taken in conjunction with the accompanying drawings.